There are numerous ways to modify polyols to improve the properties of the resultant polyurethane compositions. U.S. Pat. No. 4,535,142 generally discusses some of these methods and describes the use of diricinoleate diols for reducing the viscosity and increasing the solids content of certain polyurethane coating compositions.
Hydrocarbon polymer polyols, as defined in this application, are generally not used in coating compositions because they provide unsuitable mechanical and weathering properties as well as poor adhesion to most commonly used substrates. Furthermore, hydrocarbon polymer polyols are generally highly viscous and substantially incompatible with many low viscosity polyols that could be blended or mixed therewith to reduce their viscosity. Thus, the polyol mixture becomes cloudy, separates or forms a two-phase solution which is not suitable for further reaction as a casting or potting formulation.
A limited number of specific polyether polyols are compatible with certain hydrocarbon polymer polyols, however, blends of these polyols result in a mixture having inferior mechanical properties or much higher viscosities than can be obtained from the unmodified hydrocarbon polymer polyol alone. Therefore, it is difficult to use such mixtures in casting or potting formulations. While it is also possible to use various extender compounds such as plasticizers, oils and the like to obtain low viscosity hydrocarbon polymer polyol mixtures, this low viscosity property is achieved at the expense of mechanical properties and hydrolytic stability of the formulation.
It has now been found that the properties of hydrocarbon polymer polyols can be modified by mixing those polyols with any of a number of ricinoleate compounds having at least one and preferably two or more hydroxyl groups per molecule. These ricinoleate compounds possess very low viscosities and allow modification of the final properties of the overall polyurethane composition, while not detracting from the properties available from the hydrocarbon polyols. Thus, the substitution of these compounds for a portion of the hydrocarbon polymer polyol yields compositions having improved mechanical properties, solvent resistance, and flexibility, while maintaining the electrical properties at an acceptable level.